1. Department of Natural Resources, Cornell University, Fernow Hall, Ithaca, NY 14853, USA.
2. Department of Environmental Science, Policy and Management (E.S.P.M.), University of California at Berkeley, Berkeley, CA 94720-3114, USA.
3. Miami University, Department of Biology, Oxford, OH 45056, USA.
4. Department of Civil and Environmental Engineering, Syracuse University, Link Hall, Syracuse, NY 13244, USA.
5. LSA Earth and Environmental Science, University of Michigan, 2534 CC Little, Ann Arbor, MI 48109, USA.